Adhesive composition components such as base polymers, tackifiers, and waxes are customarily provided as separate components for formulation into hot melt adhesive (HMA) compositions. In HMA packaging applications, adhesive compositions are sought that provide a desired combination of physical properties, such as reduced set time and improved mechanical strength, including fiber tear and failure mode.
Exemplary base polymer compositions and methods of making polymer compositions for HMA applications are disclosed in U.S. Pat. Nos. 7,294,681 and 7,524,910. Various polymers described in these patents and/or produced by the methods disclosed in these patents have been sold by ExxonMobil Chemical Company as LINXAR™ polymers. In addition, the process platform described in these patents can sometimes be of limited robustness for developing new products or altering product design to satisfy customer needs.
WO Publication No. 2013/134038 discloses a method for producing a polymer blend having at least two different propylene-based polymers produced in parallel reactors. The multi-modal polymer blend has a Mw of about 10,000 g/mol to about 150,000 g/mol. When subjected to Temperature Rising Elution Fractionation, the polymer blend exhibits a first fraction that is soluble at −15° C. in xylene, the first fraction having an isotactic (mm) triad tacticity of about 70 mol % to about 90 mol %; and a second fraction that is insoluble or less soluble than the first fraction at −15° C. in xylene, the second fraction having an isotactic (mm) triad tacticity of about 85 mol % to about 98 mol %.
Tackifiers in HMA applications are generally disclosed in William C. Wake, Adhesion and the Formulation of Adhesives, pp. 190-92, 224 (2d ed. 1982) and in Michael and Irene Ash, Formulary of Adhesives and Sealants, Ch. 3 (1987). Although many different types of tackifiers are known and have been used in HMA adhesive formulations, there remains a need for tackified adhesive formulations that utilize the new base polymers to achieve equivalent or better adhesive performance attributes, including fiber tear, set time, and failure mode, to HMA adhesive formulations that are currently available.
Accordingly, the present invention is directed to a tackified adhesive compositions utilizing the new polymer blends, such that the adhesive compositions have superior fiber tear, set time, and failure mode compared to commercial HMA adhesive formulations.